1. Field of the Invention
The present invention relates to a flat panel display (FPD), and more particularly, to a flat panel display having a planar field emission source formed of a low work function material.
2. Description of the Related Art
FIG. 1 shows a conventional flat cathode ray tube. As shown in the drawing, a faceplate 1 and a back plate 3 are sealed by a sealant 5. A phosphor layer 7 and a metal film 9 are formed on an inner surface of the faceplate 1. A rear electrode 11 is formed on an inner surface of the back plate 3, which faces the inner surface of the faceplate 1. In addition, a plurality of tungsten line cathodes 13 is used as an electron emission source. A grid plate 15 and a mesh electrode 17 are disposed between the faceplate 1 and the back plate 3.
The grid plate 15 has a plurality of apertures 15a that are formed corresponding to pixels for passing electrons. First and second grid electrodes 19 and 21 are respectively formed on each surface of the grid plate 15. Each of the first and second grid electrodes 19 and 21, for example, function as scan and data electrodes.
Electrons emitted from the tungsten line cathodes 13 pass through the aperture 15a of the grid plate 15 under the control of the first and second grid electrodes 19 and 21, and land on light emitting anode to excite the phosphor layer 7 by a strong electric field applied to the metal film 9.
However, said flat cathode ray tube cannot easily be adapted for a large-sized display since the line cathodes 13 are used as the electron emission source. For a large-sized display, the line cathodes 13 need to extend the length, keeping the space between each other. Accordingly, uniformity of electron-emission and the luminescence of the phosphor layers 7 will be deteriorate because the line cathodes 13 tend to vibrate and the emission source becomes sparely distributed. Furthermore, the heat generated in the line cathodes 13 deforms the grid plate 15, resulting in misalignment of the apertures 15a and the corresponding phosphor layers 7.
To solve the above-described problems, U.S. Pat. No. 4,719,388 discloses a flat electron control device having a grid-shaped accelerator electrode disposed between wire-like cathodes and an address plate having apertures.
Although the flat electron control device has an advantage of emitting electrons under more stable conditions, it is still difficult to realize a large-sized display as it comprises a wire-like cathode.